1. Field of the Invention
This invention relates to a timer switch for use, for example, in home appliances such as ranges.
2. Prior Art
One known timer switch 100 schematically shown in FIGS. 1A to 1C comprises a cam member 101 of a generally disc-shape having a cam surface 102 at its periphery, the cam surface being stepped to provide a depressed portion 103 and a shoulder portion 104 adjacent thereto. The cam member 101 is fixedly mounted on a shaft 105 rotatably mounted on a casing (not shown). The shaft 105 is operatively connected to an electric motor M for rotation about its axis, the motor being mounted on the casing. Three electrical contact plates 106, 107, 108 of a resilient material are mounted on the casing. The first contact plate 106 is biased normally into sliding engagement with the cam surface 102 at its free end, and the second contact plate 107 is biased normally into engagement with the first contact plate 106. The motor M is driven to rotate the cam member 101 at a constant speed in a counterclockwise direction as indicated by an arrow in FIGS. 1A to 1C which show the sequence of the operation of the cam member 101. The cam member 101 continues to rotate so that the first contact plate 106 slides over the shoulder portion 104 into the depressed portion 103 whereupon the second contact plate 107 is brought into engagement with the shoulder portion 104 with the third contact plate 108 engaging the second contact plate 107. An A.C. power source 110, the three contact plates 106, 107, 108, the motor M and a load L are electrically connected to provide a circuit as shown in FIG. 2. While the first contact plate 106 engages the second contact plate 107, a circuit through the motor M is closed so that the motor M is energized to rotate the cam member 101. When the second contact plate 107 engages the third contact plate 108, a circuit through the load L is closed, and the motor M is de-energized to stop the rotation of the cam member 101. This conventional timer switch 100 has a finger grip or the like operatively connected to the cam member 101 and arranged exteriorly of the casing. The timer switch 100 is reset by angularly moving the cam member 101 about the shaft 105 from the position in FIG. 1C to the position in FIG. 1A through the finger grip. Thus, this known timer switch 100 has been found not entirely satisfactory in that the resetting can not be carried out easily.